Circuit boards are commonly used to interconnect electrical, as well as electromechanical, components with each other. Typically, the circuit board is provided with a number of traces of conductive material connecting one component to the other. For example, when interconnecting integrated circuit components, electrical traces are provided from a pin of one component to a pin of another component. The conductive traces on the circuit board are typically overlaid with an insulating material to protect the conductive trace, as well as to prevent inadvertent electrical contact between the conductive trace and any other electrical signal present on or near the circuit board. Circuit boards are oftentimes provided with multiple layers of conductive traces and insulating material to allow for the placement of more conductive traces on the circuit board, i.e., denser layout and interconnection. These "multilayer" boards allow a conductive trace in one plane to cross over or under another conductive trace in another plane (separated by the insulating material) without making electrical contact. In this way, the two traces remain electrically isolated.
Circuit boards may be made from any of a number of rigid or flexible materials. Rigid circuit boards provide mechanical stability and rigidity in that the components which are mounted to the circuit board are mounted and affixed to a rigid structure which is capable of withstanding the application of a certain amount of force without damaging the interconnection between the component and the circuit board. This is particularly crucial in the case of connectors used to interconnect the circuit board with other circuit boards or components. The components on the circuit board are typically soldered in place upon initial installation. This type of interconnection is sufficiently strong and typically able to withstand the subsequent application of force without compromising the solder connection. However, in the case of connectors, the connectors are intended to allow multiple connection/disconnection with other devices. When used with rigid circuit boards, connectors are typically soldered to the circuit board, and thus, are able to withstand the force applied to the connector during the connection/disconnection with other devices.
Conductive traces on flex circuits are typically provided by photolithographically patterning the conductive traces using a conductive ink, such as silver. Several methods have been devised for providing electrical and mechanical contact between the conductive traces on a flex circuit and other devices. One such approach dispenses with the need for a connector altogether. Instead, the flex circuit is provided with a "tail" section, i.e., a narrowed or necked-down section providing electrical contact with the conductive traces on the flex circuit. The "tail" section is then inserted into a receptacle or connector on the device which to be contacted with the flex circuit. While this approach eliminates the need for a connector on the flex circuit, and the associated problems with mounting a connector to the flex circuit, it nevertheless suffers from several disadvantages. Primarily, the "tail" section of the flex circuit is still made from the same flexible material used to fabricate the flex circuit itself, and as a result, the "tail" section does not possess the required structural rigidity needed for inserting the "tail" section into the target connector or receptacle. Although insertion of the "tail" section is still possible, repeated insertions and handling of the "tail" section oftentimes results in damage to the "tail" section.
An alternative approach to the use of the "tail" section to provide interconnection with other devices is the use of a connector mounted to the flex circuit itself. The connector provides sufficient rigidity in connecting with other devices. However, the secure mounting of connectors to flex circuits presents additional problems, even beyond those encountered with rigid circuit boards. Because flex circuit are commonly made from a very thin and flexible material such as plastic, the connector/flex circuit interface must be able to withstand the application of force, and it must be able to do so without damaging the relatively fragile material of the flex circuit itself.
One approach to mounting connectors to flex circuits involves the use of staples or other fastening devices to hold the connector and flex circuit together. In this type of connection, the contacts of the connector are aligned with the conductive traces on the flex circuit. Next, staple-like devices are inserted over each contact and each conductive trace. The staple-like devices puncture the flex circuit material and are then clamped down to hold the contact and conductive trace together, thereby providing electrical and mechanical connection between each contact and each conductive trace. The use of these staple-like devices does not provide adequate immunity against tearing of the flex circuit material whenever any force is applied to the flex circuit/connector interface. Rather, the use of staple-like devices actually increases the susceptibility to flex tearing by introducing holes in the flex circuit which negatively affect the integrity of the flex circuit material.
As discussed above, the use of staple-like devices results in low reliability contact terminations. Additionally, the use of staple-like devices is a complex and labor intensive assembly process. Further, this approach does not lend itself to easy visual inspection, since, liter alia, both the top and bottom surfaces of the flex circuit must be viewed in order to ascertain the integrity of the connection.